1. Field of the Invention
The present invention relates generally to a semiconductor device, particularly to a semiconductor device having a resistor, a bleeder resistance circuit with a resistor, and a semiconductor device having the bleeder resistance circuit.
2. Description of the Related Art
Conventionally, many resistors formed of semiconductor thin films made of polysilicon or the like and many bleeder resistance circuits with such resistors have been used, and those formed of either N-type or P-type conductive semiconductor thin films have been known. A method of obtaining a desired voltage division ratio has been known which is achieved by disconnecting a polysilicon fuse through laser trimming to vary the connection of the bleeder resistance circuit. Using them, ICs such as voltage detectors and voltage regulators have been manufactured.
In conventional thin film resistors, however, their resistance values vary when stress is imposed thereon, for instance, when they are subjected to resin packaging. Hence, in a bleeder resistance circuit, the voltage division ratio often varies after resin packaging, which has been a problem. Furthermore, when the conventional laser trimming method is employed, it has been necessary to provide a fuse to enable trimming with a laser beam besides the bleeder resistance circuit.
The present invention is intended to solve the problem described above. It is an object of the present invention to obtain a high-accuracy bleeder resistance circuit that can maintain an initial resistance value even after being packaged and can maintain an accurate voltage division ratio. It is also an object of the present invention to provide a compact high-accuracy semiconductor device such as a voltage detector or a voltage regulator without using a fuse that has been required conventionally.
A semiconductor device of the present invention employs a first means to achieve the above-mentioned objects. As the first means, resistors and a resistor of the bleeder resistance circuit with the same are formed of a P-type resistor made of a P-type semiconductor and an N-type resistor made of an N-type semiconductor. Furthermore, in the bleeder resistance circuit, a resistance value to be considered as one unit is defined by a resistance value obtained through a combination of the P-type resistor and the N-type resistor. Hence, variations in resistance value of the P-type resistor and the N-type resistor due to a piezoelectric effect are canceled out each other, which is described below.
The following description is directed to the variations in resistance value due to the piezoelectric effect and influences exerted on the bleeder resistance circuit.
When stress is applied to the resistors, the resistance values of the resistors vary due to the so-called xe2x80x9cpiezoelectric effectxe2x80x9d. However, in the P-type and N-type resistors, their resistance values vary in the opposite directions to each other. This has been confirmed through experiments conducted by the present inventors. For instance, when the resistance value of the P-type resistor decreases, that of the N-type resistor increases (the direction of the variation changes depending on the direction to which the stress is applied).
When an IC is subjected to resin packaging, stress is caused. Hence, as described above, the resistance values of the resistors vary due to the piezoelectric effect. The bleeder resistance circuit is used for obtaining an accurate voltage division ratio However, the division ratio varies since the resistance values of the respective resistors vary.
The resistor according to the present invention is formed of the P-type resistor made of a P-type semiconductor and the N-type resistor made of an N-type semiconductor. Hence, the variation in resistance value can be prevented even under stress. Furthermore, in the bleeder resistance circuit, the resistance value to be considered as one unit is defined by the resistance value obtained through the combination of the P-type resistor and the N-type resistor. Thus, even under stress, the variations in resistance value of the respective resistors can be canceled out each other, whereby an accurate voltage division ratio can be maintained.
The semiconductor device of the present invention employs a second means to achieve the above-mentioned objects As the second means, P-type resistors and N-type resistors are placed on low and high potential sides, respectively, with current prevented from flowing due to rectification of P-N junctions, and then, the rectification is damaged through irradiation of the P-N junctions of necessary resistors with a laser beam or the like to allow conduction. This permits an omission of a fuse that has been required conventionally.
The resistor of the semiconductor device according to the present invention includes the P-type resistor formed of a P-type semiconductor and the N-type resistor formed of an N-type semiconductor. Hence, even under stress caused by resin packaging or the like, the variations in resistance value of the respective resistors can be canceled out each other and an initial resistance value can be maintained. In the bleeder resistance circuit, the resistance value to be considered as one unit is defined by a resistance value obtained through the combination of the P-type resistor and the N-type resistor. Consequently, an accurate voltage division ratio can be maintained. Furthermore, the P-type resistors and the N-type resistors are placed on low and high potential sides, respectively, and the P-N junctions are irradiated with a laser bean or the like, whereby the rectification is damaged to allow conduction. Thus, a fuse that has been required conventionally can be omitted.
The use of such a bleeder resistance circuit allows a compact high-accuracy semiconductor device, for example, a voltage detector or a voltage regulator, to be obtained.